Title:
HINGED SLIDE MECHANISM
United States Patent 3728662
Abstract:
A mechanism is disclosed for mounting a circuit card cage with ready access to easily insertable and removable cards. A card cage is mounted on one side of and parallel to a support plate which may include an access aperture through which test pins and adjustment controls on the closest adjacent card may be reached. The support plate is mounted on the extending ends of a pair of telescoping slide members, the base ends of which are mounted in an electronics enclosure, adjacent one or more fixed female connector blocks into which male connector means on at least one of the circuit cards is received when the slide members are fully telescoped inwardly. The telescoping slide members have elongated transverse dimensions lying in substantially the same plane, and the terminal sections of the slide members are divided about colinear hinge axes lying in the plane, so that the coupled support plate and card cages can be rotated through a substantial angle when the slide members are fully extended.
US Patent References:
Mounting rack
Singer - November 1949 - 2486764
MULTI-PRINTED CIRCUIT ASSEMBLY
Carter et al. - May 1972 - 3662225
Supporting structure for electronic components
Stoddart et al. - March 1959 - 2880379
Printed circuit card rack assembly
Schmitz - April 1964 - 3129991
High density circuit card packaging
Williams - June 1965 - 3188524
Mounting rack
Singer - November 1949 - 2486764
MULTI-PRINTED CIRCUIT ASSEMBLY
Carter et al. - May 1972 - 3662225
Supporting structure for electronic components
Stoddart et al. - March 1959 - 2880379
Printed circuit card rack assembly
Schmitz - April 1964 - 3129991
High density circuit card packaging
Williams - June 1965 - 3188524
Application Number:
05/223881
Publication Date:
04/17/1973
Filing Date:
02/07/1972
View Patent Images:
Export Citation:
Assignee:
Ampex Corporation (Redwood City, CA)
Primary Class:
Other Classes:
361/802, 439/131, 211/41.170
International Classes:
H05K7/16; H05K7/16; H02B1/04
Field of Search:
312/320,302,334 211/41 317/11CB,11DH 339/17L,17LC,17LM,17M,75M,75MP,45M,64M
US Patent References:
Primary Examiner:
Champion, Marvin A.
Assistant Examiner:
Lewis, Terrell P.
Claims:
What is claimed is
1. A circuit card mounting and access system comprising:
2. The invention as set forth in claim 1 above, wherein said telescoping arm means lie substantially in a single plane and are elongated in a direction lying in the plane, said telescoping arm means further comprising a number of slidably telescoping sections, an outermost section including a hinge axis lying in said plane, normal to the direction of elongation of the telescoping arm means.
3. The invention as set forth in claim 2 above, wherein said telescoping arm means comprise a pair of spaced apart telescoping arms, and wherein said frame is an electronics enclosure further including support means coupled to a base of said telescoping arm means, and wherein said planar support means includes aperture means therethrough for permitting access to an interior adjacent circuit card.
4. The invention as set forth in claim 3 above, including in addition flexible connector means coupling circuits of the card cage from the terminal end thereof to the interior of the electronics enclosure in both extended and retracted positions.
5. A circuit card mounting and access assembly comprising the combination of:
6. The invention as set forth in claim 5 above, wherein the terminal slide elements expose the hinged mountings when extended beyond the adjacent slide element, and wherein said slide mechanisms comprise thin columnar elements lying essentially flat in a given plane, with the hinged mechanisms rotating about a hinged axis in the given plane that is normal to the direction of telescoping of said slide mechanisms.
7. The invention as set forth in claim 6 above, wherein said card cage has an entry-exit side for cards facing in the opposite direction as the outer ends of said telescoping slide mechanisms, and wherein at least one of the circuit cards includes male connector terminals extending from the side opposite the entry-exit side.
8. The invention as set forth in claim 7 above, wherein each of the slide mechanisms has substantially three sections, the outer section being hinged to provide substantially 180° rotation of the terminal slide element and the associated support plate, and wherein in addition said slide mechanisms include stop means for releasably holding the slide mechanisms in the extended positions.
9. The invention as set forth in claim 8 above, wherein said stop means permits detachment of the outer slide member from the remainder of the slide mechanism when released.
1. A circuit card mounting and access system comprising:
2. The invention as set forth in claim 1 above, wherein said telescoping arm means lie substantially in a single plane and are elongated in a direction lying in the plane, said telescoping arm means further comprising a number of slidably telescoping sections, an outermost section including a hinge axis lying in said plane, normal to the direction of elongation of the telescoping arm means.
3. The invention as set forth in claim 2 above, wherein said telescoping arm means comprise a pair of spaced apart telescoping arms, and wherein said frame is an electronics enclosure further including support means coupled to a base of said telescoping arm means, and wherein said planar support means includes aperture means therethrough for permitting access to an interior adjacent circuit card.
4. The invention as set forth in claim 3 above, including in addition flexible connector means coupling circuits of the card cage from the terminal end thereof to the interior of the electronics enclosure in both extended and retracted positions.
5. A circuit card mounting and access assembly comprising the combination of:
6. The invention as set forth in claim 5 above, wherein the terminal slide elements expose the hinged mountings when extended beyond the adjacent slide element, and wherein said slide mechanisms comprise thin columnar elements lying essentially flat in a given plane, with the hinged mechanisms rotating about a hinged axis in the given plane that is normal to the direction of telescoping of said slide mechanisms.
7. The invention as set forth in claim 6 above, wherein said card cage has an entry-exit side for cards facing in the opposite direction as the outer ends of said telescoping slide mechanisms, and wherein at least one of the circuit cards includes male connector terminals extending from the side opposite the entry-exit side.
8. The invention as set forth in claim 7 above, wherein each of the slide mechanisms has substantially three sections, the outer section being hinged to provide substantially 180° rotation of the terminal slide element and the associated support plate, and wherein in addition said slide mechanisms include stop means for releasably holding the slide mechanisms in the extended positions.
9. The invention as set forth in claim 8 above, wherein said stop means permits detachment of the outer slide member from the remainder of the slide mechanism when released.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to mechanisms for mounting and providing access to circuit cards.
2. History of the Prior Art
In modern electronics assemblies, individual circuit cards are typically slidably received in parallel spaced relation within what is called a card cage. The most used card cages are essentially rectangular structures having connector means at the bottom into which the circuit cards plug when inserted from the top. The circuit cards are generally quite densely stacked in this configuration. Therefore, when maintenance or testing is required, the assembly must generally be at least partially disassembled, and then later reassembled.
SUMMARY OF THE INVENTION
A circuit card mounting and access system in accordance with the invention includes a frame or cabinet having a female connector block mounted therein, a card cage assembly having male connectors printed on a card extending from an open end thereof, and a pair of multisection telescoping slide mechanisms mounted by a base section to the frame in a plane adjacent the female connector block. The card cage is mounted to a section of the slide mechanism which is outermost when extended and moves between a retracted position wherein the male connector engages the female connector block and an extended position wherein the connectors are disengaged and the card cage is free to rotate about a hinging axis in the plane.
The hinging axis is perpendicular to a longitudinal direction of extension for the telescoping slide mechanisms, the hinges being in the outermost section thereof. Rotation of the card cage permits both access to electrical pins and adjustment controls through a hole in the side of the card cage and removal of cards through the open end of the card cage without detachment of the card cage. In addition, a quick disconnect mechanism in a central section of the slide mechanism permits complete detachment of the card cage from the frame if desired.
BRIEF DESCRIPTION OF THE DRAWINGS
A better understanding of the invention may be had from a consideration of the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a perspective view, partially broken away, of a card mounting and access system having a card cage assembly slidably mounted to a frame in accordance with the invention;
FIG. 2 is a perspective view of the card mounting and access system shown in FIG. 1, showing in detail the mounting of the card cage assembly to the frame;
FIG. 3 is a perspective view of the card mounting and access system shown in FIG. 1, showing in detail the card cage assembly in a rotated position;
FIG. 4 is an end view, somewhat simplified, of a telescoping slide mechanism shown in FIG. 1 for mounting the card cage assembly to the frame, the slide mechanism being in a retracted condition;
FIG. 5 is a front view of a base member in the slide mechanism shown in FIG. 4;
FIG. 6 is an end view of the base member shown in FIG. 5;
FIG. 7 is a front view of a central slide section in the slide mechanism shown in FIG. 4;
FIG. 8 is an end view of the central slide section shown in FIG. 7;
FIG. 9 is a fragmentary sectional side view of a stop portion of the central slide section taken along line 9--9 in the direction of the arrows as shown in FIG. 7;
FIG. 10 is a fragmentary sectional side view of a latching portion of the central slide section taken along line 10--10 in the direction of the arrows as shown in FIG. 7;
FIG. 11 is a front view of a mounting assembly in the slide mechanism shown in FIG. 4;
FIG. 12 is an end view of the mounting assembly shown in FIG. 11;
FIG. 13 is a side view of the mounting assembly shown in FIG. 11; and
FIG. 14 is an alternative embodiment of a mounting member in accordance with the invention.
DETAILED DESCRIPTION
As shown in FIGS. 1, 2 and 3, a card cage mounting and access system in accordance with the invention includes a pair of parallel telescoping slide mechanisms 10, 12 mounting a printed circuit card cage 14 at their outwardly extending ends and coupled at their opposite ends to a base member 15 within a frame represented as a cabinet or electronics enclosure 16. The slide mechanisms 10, 12 are identical and retract as the card cage 14 is slid into the cabinet 16 and extend as the card cage 14 is slid out of the cabinet 16. The card cage 14 is mounted on one side of a planar support plate 17 and forms one wall thereof. The card cage 14 may be one of any of a number of conventional types arranged to slidably receive one or more printed circuit boards 18. In this example, the circuit boards 18 are slidable into and out of an open end of the card cage 14 on the cabinet 16 side, taking the position of FIG. 1 as reference. In this position, male terminal connectors 20 on one or more of the circuit boards 18 insert into mating female connectors 19 within the cabinet 16 to form a plug connection. When the slide mechanisms 10, 12 are retracted relative to the cabinet 16, the card cage 14 is constrained to a proper orientation for alignment of the plug connections 19, 20. However, when the slide mechanisms 10, 12 are extended as shown in FIG. 1, the card cage 14 is free to rotate about a hinging axis 22. By rotating the card cage 14, access to the open side of the card cage assembly 14 adjacent the printed connectors 20 for servicing or repair is greatly facilitated. In addition, quick disconnect latch mechanisms 24, 26 on the slide mechanisms 10, 12 permit complete removal of the card cage 14 from the cabinet 16 if necessary.
The telescoping slide mechanism 10 is further illustrated in a retracted condition in FIG. 4. This end view is somewhat simplified in that the illustration of latches, hinges and stops is omitted for clarity. The slide mechanism 10 includes a base assembly 30 which slidably receives a mounting assembly 32. The base assembly 30 includes a base member 34 which fastens to the base member 15 (FIG. 1) and slidably receives a central slide section 36. In turn, the central slide section 36 slidably receives the mounting assembly 32.
As shown in FIGS. 5 and 6, the base slide member 34 is an elongated channel with a C-shaped cross section including an opening 40 opposite a web member base 41. Flanges 42, 43 are coplanar with the opening 40 and extend inwardly from sides 44 and 45 which are perpendicular to the web member 41. The inward edges 46, 47 of the flanges 42, 43 respectively are somewhat spaced apart to form the opening 40. The base slide member 34 is thus a thin columnar element lying essentially flat in a given plane. Three countersunk holes 48, 49, 50 are longitudinally spaced along the web member 41 and extend therethrough. The holes 48-50 may receive flat head screws (not shown) for fastening the base member 34 to a cabinet or frame 16 (as seen in FIG. 1) without interference with colinear sliding motion of the central sliding section 36 within the base section 34. A small, raised dimple or boss 52 is positioned near an inward end 54 of the base section 34 and serves as a stop for the central sliding section 36. The web member 41 of the base section 34 also contains a rectangular aperture 56 near an outward end 58. The aperture 56 serves as one portion of the quick disconnect latching mechanism.
As shown in FIGS. 7 and 8, the central sliding section 36 is an elongated member having a generally C-shaped cross section similar to that of the base member 34. The shape of the cross section of the member 34 is that of a channel 60 having a web member 62, side members 63 and 64 and an opening 65. Flanges 66, 67 extending inwardly from the sides 63, 64 respectively are coplanar with the opening 65 and have spaced apart internal edges 68, 69. Positioned near an inward end 70 of the central slide section 36 is a stop 72 which may be a raised dimple or boss for preventing the mounting assembly 32 from sliding therepast. Positioned near an outward end 74 of the central slide section 36 is another stop 76. The stop 76 is formed by punching a semicircular break in the web member 62 and bending the internal material of the semicircle inward toward the opening 65.
A rectangular aperture 78 is located in the web member 62 for receiving a latch member 80 which is affixed to the web member by one end between the inward end 70 and the aperture 78, as by a spot weld 82. As shown in greater detail in FIG. 10, the latch 80 is a generally planar flat spring extending longitudinally from the fastening point 82 along the web member 62 towards the outward end 74. The latch 80 extends through the aperture 78 and is shaped to present a gently sloping planar surface 84 when telescoping inward within the base section 34, but a vertical surface 86 when telescoping outward as the mounting assembly 10 is extended. Thus, when the central slide section 36 is received by the base member 34 and the latch 80 engages the aperture 56, the central slide section 36 can be easily slid inward with respect to the base member 34 but outward motion is restricted unless the latch 80 is manually released.
As shown in FIGS. 11, 12 and 13, the mounting assembly 32 includes first and second elongated mounting members 90, 92 mechanically coupled in an end-to-end relationship by a hinge 94. The cross section of the mounting members 92, 94 has the shape of a channel having a web member 96, perpendicular side members 97, 98 and an opening 99 with flanges 100, 101 co-planar with the opening 99 extending outwardly from the sides 97, 98 respectively. The hinge 94 is affixed to the internal surface of the web member 96 of the mounting members 90, 92 by any suitable method such as spot welding. The web member 96 of the mounting member 92 has longitudinally spaced holes 102, 104 therethrough for bolting the mounting member 92 to the support plate 17 of the card cage 14 (FIG. 1). A spring loaded stop 106 is affixed as by spot welding near the inward end 108 of the mounting member 90 and extends toward the hinge. The stop 106 is affixed to the internal surface of the web member 96 and extends through the opening 99 to engage the stop 76 when the mounting member 90 is slidably received by the central slide member 36. Because of the gently sloping planar nature of the spring loaded stop 106, it is possible to slide the stop 106 past the stop 76 when assemblying the slide mechanism 10, but once assembled the slide mechanism cannot be disassembled by sliding the stop 106 past the stop 76 under normal conditions.
In an alternative arrangement which is shown in FIG. 14, the stop 106 fastened to mounting member 90 is replaced by a latch 110 which is shaped similar to the latch 80 shown in FIGS. 7 and 10. When the latch 110 is mounted on the mounting member 90, the central slide member 36 may be eliminated with the base assembly 30 having as its only telescoping member the base member 34 which slidably receives the mounting member 90. Under these circumstances, the aperture 56 receives the latch 110 to form the two parts of the quick disconnect latching mechanism.
Although there have been described above specific arrangements of a slide mechanism in accordance with the invention for the purpose of illustrating the manner in which the invention may be used to advantage, it will be appreciated that the invention is not limited thereto. Accordingly, any and all modifications, variations or equivalent arrangements which may occur to those skilled in the art should be considered to be within the scope of the invention.
1. Field of the Invention
This invention relates to mechanisms for mounting and providing access to circuit cards.
2. History of the Prior Art
In modern electronics assemblies, individual circuit cards are typically slidably received in parallel spaced relation within what is called a card cage. The most used card cages are essentially rectangular structures having connector means at the bottom into which the circuit cards plug when inserted from the top. The circuit cards are generally quite densely stacked in this configuration. Therefore, when maintenance or testing is required, the assembly must generally be at least partially disassembled, and then later reassembled.
SUMMARY OF THE INVENTION
A circuit card mounting and access system in accordance with the invention includes a frame or cabinet having a female connector block mounted therein, a card cage assembly having male connectors printed on a card extending from an open end thereof, and a pair of multisection telescoping slide mechanisms mounted by a base section to the frame in a plane adjacent the female connector block. The card cage is mounted to a section of the slide mechanism which is outermost when extended and moves between a retracted position wherein the male connector engages the female connector block and an extended position wherein the connectors are disengaged and the card cage is free to rotate about a hinging axis in the plane.
The hinging axis is perpendicular to a longitudinal direction of extension for the telescoping slide mechanisms, the hinges being in the outermost section thereof. Rotation of the card cage permits both access to electrical pins and adjustment controls through a hole in the side of the card cage and removal of cards through the open end of the card cage without detachment of the card cage. In addition, a quick disconnect mechanism in a central section of the slide mechanism permits complete detachment of the card cage from the frame if desired.
BRIEF DESCRIPTION OF THE DRAWINGS
A better understanding of the invention may be had from a consideration of the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a perspective view, partially broken away, of a card mounting and access system having a card cage assembly slidably mounted to a frame in accordance with the invention;
FIG. 2 is a perspective view of the card mounting and access system shown in FIG. 1, showing in detail the mounting of the card cage assembly to the frame;
FIG. 3 is a perspective view of the card mounting and access system shown in FIG. 1, showing in detail the card cage assembly in a rotated position;
FIG. 4 is an end view, somewhat simplified, of a telescoping slide mechanism shown in FIG. 1 for mounting the card cage assembly to the frame, the slide mechanism being in a retracted condition;
FIG. 5 is a front view of a base member in the slide mechanism shown in FIG. 4;
FIG. 6 is an end view of the base member shown in FIG. 5;
FIG. 7 is a front view of a central slide section in the slide mechanism shown in FIG. 4;
FIG. 8 is an end view of the central slide section shown in FIG. 7;
FIG. 9 is a fragmentary sectional side view of a stop portion of the central slide section taken along line 9--9 in the direction of the arrows as shown in FIG. 7;
FIG. 10 is a fragmentary sectional side view of a latching portion of the central slide section taken along line 10--10 in the direction of the arrows as shown in FIG. 7;
FIG. 11 is a front view of a mounting assembly in the slide mechanism shown in FIG. 4;
FIG. 12 is an end view of the mounting assembly shown in FIG. 11;
FIG. 13 is a side view of the mounting assembly shown in FIG. 11; and
FIG. 14 is an alternative embodiment of a mounting member in accordance with the invention.
DETAILED DESCRIPTION
As shown in FIGS. 1, 2 and 3, a card cage mounting and access system in accordance with the invention includes a pair of parallel telescoping slide mechanisms 10, 12 mounting a printed circuit card cage 14 at their outwardly extending ends and coupled at their opposite ends to a base member 15 within a frame represented as a cabinet or electronics enclosure 16. The slide mechanisms 10, 12 are identical and retract as the card cage 14 is slid into the cabinet 16 and extend as the card cage 14 is slid out of the cabinet 16. The card cage 14 is mounted on one side of a planar support plate 17 and forms one wall thereof. The card cage 14 may be one of any of a number of conventional types arranged to slidably receive one or more printed circuit boards 18. In this example, the circuit boards 18 are slidable into and out of an open end of the card cage 14 on the cabinet 16 side, taking the position of FIG. 1 as reference. In this position, male terminal connectors 20 on one or more of the circuit boards 18 insert into mating female connectors 19 within the cabinet 16 to form a plug connection. When the slide mechanisms 10, 12 are retracted relative to the cabinet 16, the card cage 14 is constrained to a proper orientation for alignment of the plug connections 19, 20. However, when the slide mechanisms 10, 12 are extended as shown in FIG. 1, the card cage 14 is free to rotate about a hinging axis 22. By rotating the card cage 14, access to the open side of the card cage assembly 14 adjacent the printed connectors 20 for servicing or repair is greatly facilitated. In addition, quick disconnect latch mechanisms 24, 26 on the slide mechanisms 10, 12 permit complete removal of the card cage 14 from the cabinet 16 if necessary.
The telescoping slide mechanism 10 is further illustrated in a retracted condition in FIG. 4. This end view is somewhat simplified in that the illustration of latches, hinges and stops is omitted for clarity. The slide mechanism 10 includes a base assembly 30 which slidably receives a mounting assembly 32. The base assembly 30 includes a base member 34 which fastens to the base member 15 (FIG. 1) and slidably receives a central slide section 36. In turn, the central slide section 36 slidably receives the mounting assembly 32.
As shown in FIGS. 5 and 6, the base slide member 34 is an elongated channel with a C-shaped cross section including an opening 40 opposite a web member base 41. Flanges 42, 43 are coplanar with the opening 40 and extend inwardly from sides 44 and 45 which are perpendicular to the web member 41. The inward edges 46, 47 of the flanges 42, 43 respectively are somewhat spaced apart to form the opening 40. The base slide member 34 is thus a thin columnar element lying essentially flat in a given plane. Three countersunk holes 48, 49, 50 are longitudinally spaced along the web member 41 and extend therethrough. The holes 48-50 may receive flat head screws (not shown) for fastening the base member 34 to a cabinet or frame 16 (as seen in FIG. 1) without interference with colinear sliding motion of the central sliding section 36 within the base section 34. A small, raised dimple or boss 52 is positioned near an inward end 54 of the base section 34 and serves as a stop for the central sliding section 36. The web member 41 of the base section 34 also contains a rectangular aperture 56 near an outward end 58. The aperture 56 serves as one portion of the quick disconnect latching mechanism.
As shown in FIGS. 7 and 8, the central sliding section 36 is an elongated member having a generally C-shaped cross section similar to that of the base member 34. The shape of the cross section of the member 34 is that of a channel 60 having a web member 62, side members 63 and 64 and an opening 65. Flanges 66, 67 extending inwardly from the sides 63, 64 respectively are coplanar with the opening 65 and have spaced apart internal edges 68, 69. Positioned near an inward end 70 of the central slide section 36 is a stop 72 which may be a raised dimple or boss for preventing the mounting assembly 32 from sliding therepast. Positioned near an outward end 74 of the central slide section 36 is another stop 76. The stop 76 is formed by punching a semicircular break in the web member 62 and bending the internal material of the semicircle inward toward the opening 65.
A rectangular aperture 78 is located in the web member 62 for receiving a latch member 80 which is affixed to the web member by one end between the inward end 70 and the aperture 78, as by a spot weld 82. As shown in greater detail in FIG. 10, the latch 80 is a generally planar flat spring extending longitudinally from the fastening point 82 along the web member 62 towards the outward end 74. The latch 80 extends through the aperture 78 and is shaped to present a gently sloping planar surface 84 when telescoping inward within the base section 34, but a vertical surface 86 when telescoping outward as the mounting assembly 10 is extended. Thus, when the central slide section 36 is received by the base member 34 and the latch 80 engages the aperture 56, the central slide section 36 can be easily slid inward with respect to the base member 34 but outward motion is restricted unless the latch 80 is manually released.
As shown in FIGS. 11, 12 and 13, the mounting assembly 32 includes first and second elongated mounting members 90, 92 mechanically coupled in an end-to-end relationship by a hinge 94. The cross section of the mounting members 92, 94 has the shape of a channel having a web member 96, perpendicular side members 97, 98 and an opening 99 with flanges 100, 101 co-planar with the opening 99 extending outwardly from the sides 97, 98 respectively. The hinge 94 is affixed to the internal surface of the web member 96 of the mounting members 90, 92 by any suitable method such as spot welding. The web member 96 of the mounting member 92 has longitudinally spaced holes 102, 104 therethrough for bolting the mounting member 92 to the support plate 17 of the card cage 14 (FIG. 1). A spring loaded stop 106 is affixed as by spot welding near the inward end 108 of the mounting member 90 and extends toward the hinge. The stop 106 is affixed to the internal surface of the web member 96 and extends through the opening 99 to engage the stop 76 when the mounting member 90 is slidably received by the central slide member 36. Because of the gently sloping planar nature of the spring loaded stop 106, it is possible to slide the stop 106 past the stop 76 when assemblying the slide mechanism 10, but once assembled the slide mechanism cannot be disassembled by sliding the stop 106 past the stop 76 under normal conditions.
In an alternative arrangement which is shown in FIG. 14, the stop 106 fastened to mounting member 90 is replaced by a latch 110 which is shaped similar to the latch 80 shown in FIGS. 7 and 10. When the latch 110 is mounted on the mounting member 90, the central slide member 36 may be eliminated with the base assembly 30 having as its only telescoping member the base member 34 which slidably receives the mounting member 90. Under these circumstances, the aperture 56 receives the latch 110 to form the two parts of the quick disconnect latching mechanism.
Although there have been described above specific arrangements of a slide mechanism in accordance with the invention for the purpose of illustrating the manner in which the invention may be used to advantage, it will be appreciated that the invention is not limited thereto. Accordingly, any and all modifications, variations or equivalent arrangements which may occur to those skilled in the art should be considered to be within the scope of the invention.